1. Field of the Invention
This invention relates generally to air suspension trailer dump systems and particularly to stabilizing devices therefor.
2. Brief Description of the Prior Art
Dump trailers have traditionally used conventional single point two spring suspension systems. This standard leaf spring design provides relatively good stability during dumping operations because of its inherent stiffness. However, the inherent stiffness of this design also yields the disadvantage of a choppy and uncomfortable ride.
The use of air spring suspension systems for trailers yielded a much smoother and more comfortable ride. However, because of the inherent softness of air springs, there was created a degree of load instability during dumping operations which has caused a number of trailers to overturn during such activity. This instability is created by load transfer from the trailer to the wheels through the inherently soft air springs. One means of accomplishing this in the prior art was to provide rubber spacers within the air springs thus adding firmness to the suspension system during dumping. However, although such a design did add some firmness, the instability, to a large degree was still present. Further, the addition of rubber spacers resulted in an increase in air spring failures.
Another method in the prior art for reducing instability was to provide a travel stop on the pivot arm typically used in air spring suspension systems. The pivot arm is mounted to a hanger by bushings, the hanger extending downward from the frame of the trailer. The air springs reside between the pivot arm and the frame of the trailer and the trailer axle resides in close proximity to the air springs and is attached by some means to the pivot arm. The pivot arm travel stops of the prior art were typically bumpers mounted to the frame of the trailer midway between the air springs and the bushing connecting the hanger to the pivot arm. During dumping operation, as the air spring collapsed over the load, the pivot arm would pivot upward toward the frame and would contact the bumper. This design served to increase stability during dumping operations to a large degree. However, this was not accomplished without a price. The placement of the bumper at a point intermediate to the air spring and the bushing connecting the hanger to the pivot arm resulted in the bushing absorbing a great deal of the load transferred from the trailer frame to the wheels of the trailer. Wear and tear on the bushing became greater requiring that such bushing be replaced often.
U.S. Pat. No. 2,859,047 to Easton teaches a stabilizer arrangement for a pneumatic suspension system. However, the Easton design is directed to restraining lateral movement of the air cells when the vehicle is making a sharp turn. As such, the Easton design does not teach anything structurally or functionally similar to the invention described in the present application which is directed to stabilizing an air spring suspension trailer during dumping operations.
U.S. Pat. No. 4,309,045 to Raidel teaches an air suspension assembly for heavy duty trucks. The Raidel design is directed to a paralellogram type of axle stabilization. It is not directed to removing load from the air springs during dumping operations and as such, Raidel teaches nothing structurally or functionally similar to the design of the present invention.